If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Siwa: The hottest months are usually July and August with an average temp of 86°F, while the coldest months are January and February with an average of 59°F. From January through March, the daytime average is 76°F and the nighttime average is 47°F. Between April and June, temperatures average 98°F during the day and 62°F at night. July through September averages 100°F during the day and 72°F at night. In October-December, the average temperature is 85°F during the day and 51°F at night.